Object that rotates in a flow of air, suitable for recreational use

ABSTRACT

An object intended to rotate in a flow of air (F), comprising a plate ( 2 ) with a general planar aspect and globally extending along a plane, the plate ( 2 ) comprising: a rear face ( 4 ) having a central area ( 16 ) on which an operator ( 6 ) is intended to exert a pressure force (F 1 ) either directly or via a support; a front face ( 8 ) intended to receive the flow of air; a peripheral portion ( 10 ); and a main portion ( 14 ) extending between the peripheral portion; the plate having a stable shape at rest, the plate having a shape in use such that:
         the pressure force balances a resulting force (F 2 ) exerted by the flow of air on the plate, so that the central area remains in contact with the operator or the support, and   the flow of air exerts a torque on the plate causing rotation of the plate around an axis substantially perpendicular to the plane.

The present invention relates to an object intended to rotate in a flow of air notably for recreational use.

There exist different objects for which the recreational function is based on the rotation around a material or immaterial axis. Let us mention for example:

the ball laid on one finger and driven into rotation by means of the other hand,

-   -   the so-called <<Chinese>> plates, driven into rotation by an         alternating movement of sticks oriented skywards,     -   spinning tops, laid on a supporting surface, for which the         contact point and the axis precession follow an <<erratic>>         time-dependent movement and for which rotation is limited in         time,     -   the wind turbine-propeller axially mounted on a shaft.

An object of the invention is to provide an alternating object including at least one portion driven into rotation by a flow of incident air, unlike the mass balloon or the <<Chinese>> plates, and which has a very simple lightweight and not very bulky structure which may immediately be used.

For this purpose, the invention relates to an object intended to rotate in a flow of air, notably for recreational use, comprising a plate with a general planar aspect extending globally along a plane, the plate having a center of inertia and comprising:

-   -   a rear face including a central area rotated in the vicinity of         the center of inertia, on which an operator is intended to exert         a pressure force, directly or via a support, during periods of         use of the object;     -   a front face intended to receive the flow of air substantially         along an axis passing through the center of inertia and         perpendicular to the plane;     -   a peripheral portion encompassing an edge of the plate; and     -   a main portion extending between the peripheral portion and         including the central area;         the plate having a stable shape at rest, which may be piled up,         and having this shape after each of the periods of use,         the plate having, during any of the periods of use, a shape in         use such that:     -   the pressure force exerted by the operator balances a resulting         force exerted by the flow of air on the plate, so that the         central area remains in contact with the operator or the         support, and     -   the flow of air exerts a torque on the plate causing the plate         to rotate substantially around the axis.

According to particular embodiments, the object may comprise one or more of the following features, taken individually or according to all the technically possible combinations:

-   -   the plate, on at least 90% of the surface area of the rear face,         has a thickness comprised between 5 and 500 μm, preferably         between 10 and 200 μm, and a basis weight comprised between 10         and 200 g/m², preferably between 20 and 100 g/m² ;     -   the peripheral portion of the plate comprises one or several         areas which cannot be developed;     -   the peripheral portion comprises at least one area forming with         the plane, at rest, an average angle greater than or equal to         10°, preferably greater than or equal to 30°;     -   the plate comprises at rest at least one convex area, the         convexity of which is oriented from the front face to the rear         face, and at least one other convex area for which the convexity         is turned from the rear face to the front face, so that the         plate may be reversibly used by the operator;     -   the plate, in order to pass from the position at rest to the         position of use, undergoes flexure along a weakness axis;     -   the shape at rest of the plate is such that, if the plate         retained the shape at rest during the period of use, the air         flow would not be able to rotate the plate substantially about         the axis;     -   the plate, in an orthogonal projection on the plane,         substantially has a general shape assumed from among the         following shapes: triangular, rectangular, parallelogram,         trapezoidal shape, four-sided and convex, four-sided and concave         with the center of inertia being located inside the         quadrilateral, convex polygonal, star-shaped polygonal with the         center of inertia being located inside the star-shaped polygon;     -   the plate, in an orthogonal projection on the plane, has a         polygonal shape including sides substantially of a rectilinear,         concave, convex, <<S-shaped>>, or toothed shape;     -   the plate is in plastic polymer, in bio-plastic polymer, in a         laminated material comprising a plastic polymer and a         bio-plastic polymer, or in tissue paper.

The invention will be better understood upon reading the description which follows, only given as an example, and made with reference to the appended drawings, wherein:

FIG. 1 schematically illustrates in a perspective view, an object according to the invention in its rest position,

FIG. 2 schematically illustrates in a front view, the object illustrated in FIG. 1,

FIG. 3 schematically illustrates in a side view, the object illustrated in FIG. 1,

FIGS. 4, 5 and 6 schematically illustrate sectional views of the object illustrated in FIG. 1 along planes IV-IV to VI-VI of FIG. 2, substantially orthogonal to the plane along which extends the object and respectively passing through a longitudinal axis, a transverse axis and a diagonal axis of the object,

FIG. 7 schematically illustrates the operation of the object illustrated in FIG. 1,

FIG. 8 shows a sectional view of the object illustrated in FIG. 7, along the plane VIII-VIII of FIG. 2 perpendicular to the plane along which extends the object,

FIG. 9 schematically illustrates in a front view an alternative of the object illustrated in FIGS. 1 to 6,

FIG. 10 schematically illustrates in a front view an object illustrating a second embodiment of the invention,

FIG. 11 provides a sectional view of the object illustrated in FIG. 10, along the plane XI-XI of FIG. 10, substantially orthogonal to the plane along which extends the object and passing through a longitudinal axis of the object,

FIG. 12, views A to E,

FIG. 13, views A to E,

FIGS. 14, 15, views A and B and

FIGS. 16 and 17 each schematically illustrate a shape which an object according to the invention may have at rest, as a projection on the plane along which it extends.

With reference to FIGS. 1 to 6, an object 1 forming a toy is described.

The object 1 consists of a single part with the general shape of a plate 2.

The plate 2 has a general planar aspect, for example in the shape of a tray. By convenience, the structure of the plate 2 laid on a horizontal plane P1 will be described, the bottom of the tray being turned towards the plane P1.

By <<general planar aspect>> is meant that, as the plate 2 has a maximum dimension d in space (FIG. 2), the plate 2 is comprised between the plane P1 and a plane P2, parallel to the plane P1, located at a distance d′ from the plane P1, less than or equal to d/3, preferably less than or equal to d/5 and even more preferably less than or equal to d/10.

The plane 2 has a center of inertia I. Because of the tray shape, the center of inertia I is not located in the plate 2, but is slightly above.

A plane P is defined, passing through the center of inertia I of the plate 2, secured to the plate 2 and parallel to the plane P1 when the plate 2 is laid on the plane P1 (FIG. 3). The plate 2, being of a general planar aspect, extends along the plane P. In an orthogonal projection on the plane P, the plate 2 has a general rectangular shape visible in FIG. 2 and in FIG. 12A, with four rounded corners and four concave sides.

An axis Iz is further defined, perpendicular to the plane P, passing through the center of inertia I and oriented upwards, the plate 2 having a height h along the Iz axis. The plate 2 extends along a longitudinal direction Ix perpendicular to the Iz axis, with a length L1. The plate 2 extends along a transverse direction Iy perpendicular to the longitudinal direction Ix and to the axis Iz, with a width L2. The center of inertia I, the axis Iz and the directions Ix and Iy define an orthonormal reference system (I, Ix, Iy, Iz). The planes P and (xIy) coincide. When the plate 2 is laid on the plane P1, the planes P and (xIy) are horizontal and the Iz axis is vertical.

The ratio L1/L2 is comprised between 1.0 and 2.0, preferably between 1.2 and 1.8, advantageously it has a value of about 1.5.

The ratio L1/h is comprised between 5 and 500 and for example has the value of about 13.

For example L1 is comprised between 5 and 15 cm and advantageously has the value of about 9 cm; L2 is comprised between 3 and 10 cm and advantageously has the value of about 5 cm. h is comprised between 0.5 and 2 cm and advantageously has the value of 1.0 cm.

The plate 2 has a shape at rest and resumes this shape after each of the periods of use. This shape at rest will now be described.

By <<shape at rest>>, is meant a shape assumed by the plate 2 out of the periods of use, for example when the plate 2 is laid on the plane P1, the bottom of the tray resting on the plane P1. The plate 2 is conformed so as to return to this rest position after each of the periods of use, in the absence of any particular urge.

The shape at rest may advantageously be piled up. By <<may be piled up>> is meant that the plate 2 may be stacked, for example along the Iz axis, with other plates having the same shape as the plate 2, in the same way as identical trays are stacked.

In the shape at rest illustrated in FIGS. 1 to 6, the plate 2 is substantially symmetrical relatively to the planes (xIz) and (yIz).

The plate 2 advantageously has a material thickness e (FIG. 4) comprised between 5 and 500 μm, preferably between 10 and 200 μm. The plate 2 for example has a basis weight comprised between 10 and 200 g/m², preferably between 20 and 100 g/m².

The plate 2 is for example in a plastic or thermoplastic polymer, of fossil or plant origin (for example in polyolefin or polyester), or in a laminated material comprising such a polymer. The plate is then for example made by thermoforming or any other compliant method, or further for example by assembling portions. Alternatively, the plate may be in a cellulose material (for example in tissue paper), in a composite material or in other materials having shape stability at rest.

According to a particular embodiment, the plate 2 may have electrostatic properties so that the plate 2 may remain stuck on a wall.

The plate 2 comprises a rear face 4, located on the back of the tray, on which an operator 6 is intended to apply a pressure force F1 (FIG. 4) during the periods of use, and a front face 8, located in the tray, intended to receive a flow of air F during the periods of use.

The plate 2 further comprises a flared peripheral portion 10, encompassing an edge 12 of the plate 2, and a main planar portion 14 formed by the plate 2 deprived of the peripheral portion 10.

The rear face 4 comprises a central area 16, located in proximity to the center of inertia I, on which the pressure force F1 exerted by the operator 6 is intended to be applied. The rear face 4 extends on both the peripheral portion 10 and on the main portion 14, the central area 16 of the rear face 4 being found in the main portion 14 of the plate 2.

The rear face 4 may for example be defined by an equation of the z=f(x,y) type in the reference system (I, Ix, Iy, Iz).

The central area 16 of the rear face 4 for example substantially forms a disc having as a center a point I′ corresponding to the projection of the center of inertia I on the rear face 4 along the axis Iz and having a radius R, for example of about 1 cm.

Also, the front face 8 extends both on the peripheral portion 10 and on the main portion 14 of the plate 2.

The main portion 14 corresponds to the bottom of the tray in contact with the plane P1. The main portion 14 is substantially planar. Alternatively, the main portion 14 may be either convex or concave. For example the main portion 14 may have a positive or negative deflection along the Iz axis comprised between 0 and h/2.

The peripheral portion 10 surrounds the main portion 14 and forms, by raising the plate 2 upwards, the sides of the tray. The peripheral portion 10 comprises four sides 18, 20, 22, 24 and four corners 26, 28, 30, 32 each located between two of the four sides.

The sides 18, 20 extend along the longitudinal direction Ix and are substantially symmetrical relatively to the plane (xIz). The sides 22, 24 extend along the transverse direction Iy and are substantially symmetrical to the plane (yIz). Also, only the sides 18 and 22 will be described in detail.

If one excludes the thickness e of the plate 2, the side 18 is in contact with the corner 26 along a line 34 and symmetrically with the corner 28 along a line 36. The side 18 is further in contact with the main portion 14 along a line 38. The side 18 comprises an upper edge 40 forming a fraction of the edge 12 of the plate 2.

Also, the side 22 is in contact with the corner 26 along a line 42 and symmetrically, with the corner 32 along a line 44. The side 22 is further in contact with the main portion 14 along a line 46. The side 22 comprises an upper edge 48 forming a fraction of the edge 12 of the plate 2.

The upper edges 40, 46 and the contact lines 38, 46 between the sides 18 and 22 and the main portion 14, in an orthogonal projection on the plane P, advantageously have convexity turned towards the point I.

The sides 18 and 22 have an average tilt α with the plane P comprised between 30 and 90°, for example about 60° (FIGS. 4 and 5).

The corners 26, 28, 30, 32 are each located in one of the quadrants defined by the longitudinal direction Ix and the transverse direction Iy. The corners 28, 30, 32 are inferred from the corner 26 by symmetries relatively to the planes (xIz) and (yIz), therefore only the corner 26 will be described in detail.

The corner 26 advantageously has convexity turned towards the outside of the tray. The corner 26 is in contact with the side 18 along the line 34, with the side 22 along the line 42 and with the main portion 14 along a line 50. The corner 26 further comprises an upper edge 52 which, in an orthogonal projection on the plane P, has concavity towards the center of inertia I. In other words, the upper edge 52 of the corner 26 forms a rounded edge connecting the upper edge 40 of the side 18 to the upper edge 48 of the side 22.

The contact lines 38 and 46 between the sides 18 and 22 and the main portion 14 correspond to areas where the curvature of the plate 2 is maximum. The lines 38 and 46 form blunt edges or <<pseudo-edges>>.

The contact lines 34 and 42 between the corner 26 and the sides 18 and 22 also correspond to areas where the curvature of the plate 2 is maximum. The lines 34 and 42 therefore also form blunt edges or <<pseudo-edges>>.

Alternatively, the lines 34 and 42 may correspond to areas where the local curvature of the plate 2 is zero, i.e. at inflection points of the peripheral portion. The passage between the sides 18 and 22, of concave aspect, and the corner 26 of convex aspect, is then ensured without any edge.

The contact line 50 between the corner 26 and the main portion 14 corresponds to points where a variation in the curvature of the plate 2 occurs, the curvature being small in the main portion 14 and becoming stronger in the corner 26 (FIG. 6).

Alternatively, the line 50 may correspond to an area where the curvature of the plate 2 is maximum. The line 50 then forms a blunt edge or <<pseudo-edge>>.

Depending on the relevant alternatives for the lines 34, 42 and 50 delimiting the corner 26, these lines are either apparent or not, as edges or pseudo-edges.

Further, the line 38 advantageously has a local maximum of curvature of the plate 2 located in the plane (yIz). Also, the line 46 advantageously has a local maximum of curvature of the plate 2 located in the plane (xIz). In other words, the pseudo-edges between the sides 18 and 22 and the main portion 14 are sharper towards the middle of the sides 18 and 22 and more rounded upon moving gradually closer to the corners 26, 28, 32.

It is understood that the peripheral portion 10 comprises many curved areas and which cannot be developed. By <<area which cannot be developed>> is meant an area which cannot be flattened on the plane P1 without damaging it, either by denting it or by tearing it. The corners 26, 28, 30, 32 are typically areas which cannot be developed.

The plate 2 is moreover conformed so as to resist differently to a flexural moment M around an axis D passing through the center of inertia I and belonging to the plane P, depending on an angle θ formed between the direction Ix and the axis D in the plane P (FIG. 2). For example, the plate 2 has two diagonal weakness axes D1 and D2. More specifically, D1 passes through the corners 26 and 30 and D2 passes through the corners 28 and 32.

Thus, the plate 2 may flex according to either one of the axes D1 or D2, for example the axis D1 and adopt a shape in use illustrated in FIGS. 7 and 8, wherein the plate 2 is no longer made in the horizontal plane P1.

In the shape in use, a first half 54 of the plate 2, located on the side of the corner 28 relatively to the axis D1 or D2, and a second half 56 of the plate 2, located on the side of the corner 32 relatively to the same axis, each form an angle φ with the plane P in the direction of the negative values of the axis Iz (FIG. 8).

The angle φ is for example comprised between 0° and 45°, advantageously between 0.5° and 15°.

It is understood that, even if the angle φ is relatively small, optionally perceivable with difficulty with the naked eye, it is nevertheless sufficient so that the plate 2 substantially no longer has the symmetries mentioned earlier relatively to the planes (xIz) and (yIz).

The operation of the object 1 will now be described hereafter, notably with reference to FIGS. 7 and 8.

Out of the periods of use, the plate 2, in the absence of any particular urge, substantially has the shape at rest as described above. The plate 2 may be arranged alone or stacked with other similar plates.

During any of the periods of use, the operator 6 places the plate 2 for example on the end 58 of a finger and starts to exert a pressure force F1 on the central area 16, for example by pushing the central area 16 with the forefinger so as to impart to the plate 2 a velocity v substantially oriented along the Iz axis, in the direction of positive values. The contact between the end of the finger 58 and the plate 2 is close to a sphere-plane contact. Alternatively, the operator 6 may indirectly exert the pressure force F1 via a support (not shown) such as a stick including a suitable endpiece in contact with the central area 16.

Because of the velocity v acquired by the plate 2, the front face 8 receives a flow of air F generated by the relative displacement of the plate 2 relatively to ambient air.

The flow of air F exerts forces on the plate 2 which are notably expressed by a resulting force F2 substantially opposing the pressure force F1 exerted by the operator. The pressure force F1 exerted by the operator, the resulting force F2 and the weight of the plate 2 substantially balance each other, so that the plate 2 is held at the end 58 of the finger of the operator 6. In the absence of this resulting force F2, the plate 2 would fall under the action of its own weight.

The forces exerted by the air also urge the plate 2 in flexure, the plate 2 bearing upon the finger of the operator 6. Thus, very rapidly, the plate 2 flexes along either one of the weakness axes D1 or D2, for example D1. The plate 2 then assumes the shape in use described above.

The flow of air F splits up on either side of the axes D1 and flows on the first half 54 and on the second half 56 of the plate 2. The flow of air F is then diverted by the peripheral portion 10 of the plate 2, before escaping. Because of the shape in use of the plate 2, the flow of air F also exerts on the plate 2 a torque causing rotation of the plate 2 substantially around the axis Iz. This rotational movement also contributes to stabilizing the plate 2 on the end 58 of the finger of the operator by a gyroscopic effect.

Thus, in use, the plate 2 freely and continuously rotates on the end 58 of the finger of the operator 6 substantially around the Iz axis. The plate 2 is capable of being held on the end of the finger of the operator 6 for an arbitrarily long duration, for example a few minutes.

A role of the main portion 14 is to provide on the rear face 4 a supporting area for the operator 6 located in the central area 16, while the peripheral portion 10 gives the possibility of obtaining some stiffness of the plate 2 and of defining at least the flexural weakness axis D1.

The main portion 14 and the peripheral portion 10 divert the flow of air F and allow it to exert a torque on the plate 2 relatively to the Iz axis. The central area 16 thus remains in contact with the finger of the operator 6 for the period of use, the plate 2 substantially rotating around the axis Iz.

The plate 2 is conformed so that, when the operator 6 pushes the plate 2 vertically downwards with a velocity v greater than a minimum velocity v0, the central area 16 remains in contact with the finger of the operator 6 or the support, the plate 2 substantially rotating around the Iz axis. The plate 2 is advantageously conformed so that the minimum velocity V0 is less than 3.0 m/s, preferably less than 1.5 m/s and even more preferably less than 1.0 m/s.

Further it is possible for the operator 6 to impart to the center of inertia I a certain trajectory 60, for example a curve trajectory, by modifying the exerted pressure force F1 (FIG. 7).

Thus, in order to increase the duration of the period of use, the operator 6 may for example rotate on himself/herself and impart to the center of inertia I of the plate 2 a circular movement parallel to the ground.

Alternatively, the operator 6 may impart to the center of inertia I a substantially vertical and rectilinear trajectory, including downwards, or else with optional U-turns and round trips, or further with the shape of an <<8>>.

According to another method of use, the operator 6 may place the plate 2 in a pre-existing flow of air F, for example, wind, or an air jet produced by a fan and by the pressure force F1 exerted on the central area 16, may maintain the plate 2 in the flow of air F, the plate 2 starting to rotate around the Iz axis.

After the period of use, the plate 2 substantially resumes the shape at rest described above. The plate 2 may again be arranged, alone or stacked with other similar plates, for example in a box comprising two suitable portions at the rear face 4 and at the front face 8 of the plate 2 respectively.

Thus, by means of the features described above, notably the shape at rest and the capability of having a shape during use on which the flow of air F exerts a torque relatively to the axis Iz, the object 1 is driven into rotation by an incident air flow. Further, as the operator 6 does not need to modify the object 1 and that the plate 2 resumes its shape after each use, the object 1 remains immediately usable.

Generally, it is understood that the behavior during use of the plate 2 depends on a large number of parameters related together, such as shape, distribution of the mass, mechanical strength, surface properties of the central area 16 . . . Thus, for example the flexural strength of the plate 2 along the weakness axis D1 is sufficiently low so that the plate 2 flexes in the flow of air F, but is sufficiently strong so that the plate 2 does not flex too much, which would generate friction against the finger of the user 6 and would prevent rotation of the plate 2. Now, the flexural strength notably depends on the shape, on the dimensions and on the material of the plate 2. These interdependent parameters may be adapted by one skilled in the art in order to obtain such and such particular effect, for example more or less great ease in using the object 1, a more or less rapid rotation of the plate 2 . . . etc.

An alternative of the object 1 will now be described, formed by the object 101 illustrated in FIG. 9. The object 101, if not specified otherwise, is similar to the object 1.

The object 101 differs from the object 1 mainly by the shape of the contact lines 38, 46, 52 which all form edges, i.e. areas of strong curvature of the plate 2.

Further, the corners 26, 28, 30, 32 are substantially planar, so as to form facets.

This gives the plate 2 a more rectilinear aspect, with, in a front view (FIG. 9), corners with a rectilinear edge.

The plate 2 of the object 101 retains the two weakness axes D1 and D2 and operates similarly to the object 1.

A second embodiment of the invention will now be described, formed by the object 201 illustrated in FIGS. 10 and 11. Many portions of the object 201, except if specified otherwise, are similar to those of the object 101 of FIG. 9, bear the same alphanumerical references and will not be described again. For this description the axis Iz is oriented downwards.

The object 201 differs from the object 101 in that it includes a peripheral portion 210 integrating a first portion 211 similar to the peripheral portions 10 of the object 101 and a second portion 212 surrounding the first portion 211.

If the first portion 211 corresponds, as this has been seen, to a raising of the plate 2 by a height h in the direction of the positive values of the Iz axis, the second portion 212 corresponds to a lowering, also by a height h, in the direction of the negative values of the Iz axis. The peripheral portion 210 thus forms a <<V-gutter>> around the main portion 14 when the plate 2 is oriented so that the axis Iz points downwards (FIG. 10).

The peripheral portion 210 therefore has convexity turned in the direction of the positive values of the Iz axis.

The assembly formed by the main portion 14 and the first portion 211 on the other hand has convexity turned in the direction of the negative values of the Iz axis.

The second portion 212 comprises four sides 218, 220, 222, 224 and four corners 226, 228, 230, 232 connected together in a similar way to the sides 18, 20, 22, 24 and to the corners 26, 28, 30, 32 of the first portion 10.

Each corner 226, 228, 230, 232 of the second portion 212 has an edge, in the form of a sharp edge, common with the corner 26, 28, 30, 32 of the first portion 211 having a numerical reference of less than 200. Each corner 226, 228, 230, 232 of the second portion 212 is tilted relatively to the plane P in an opposite way to the corner 26, 28, 30, 32 of the first portion 211 having a numerical reference less than its own by 200.

Also, each side 218, 220, 222, 224 of the second portion 212 has an edge in the form of a sharp edge, common with the side 18, 20, 22, 24 of the first portion 211 having a numerical reference less than 200. Each side 218, 220, 222, 224 of the second portion is tilted relatively to the plane P in an opposite way to the side 18, 20, 22, 24 of the first portion 211 having a numerical reference less than its own by 200.

The plate 2 retains both diagonal weakness axes D1 and D2.

The object 201 may operate in a similar way to the object 1, the second portion 212 not perturbing the flow of air F in a significant way.

Further, the object 201 is reversible, in the sense that it may be used by reversing the roles of the front face 8 of the rear face 4. In other words, the operator 6 may lay his/her finger on the front face 8, at right angles to the central area 16, the rear face 4 for receiving the flow of air F. The plate 2 then starts to rotate around the axis Iz, since the gutter shape of the peripheral portion 210 is such that the flow of air exerts a torque on the plate 2.

The plate 2 of the objects, 1, 101, 201 may be made in a wide variety of general shapes, such as those illustrated in FIGS. 12 to 17. These general shapes are orthogonal projections of the edge 12 of the plate 2 on the plane P.

FIG. 12 includes views from A to E illustrating shapes derived from the rectangle. Their sides may have a rectilinear, concave, convex, <<S>>, or toothed shape, or juxtapositions of these shapes.

View A shows a shape 301 substantially corresponding to the general shape of the plate 2 of the object 1, while view D shows a shape 304 substantially corresponding to the general shape of the plate 2 of the objects 101 and 201.

FIG. 13 includes views A to E illustrating general shapes derived from the parallelogram. Such shapes also have two weakness axes D1 and D2 with regard to flexural stress, but the axis D2, extending along the smallest diagonal is generally the weakest.

FIG. 14 illustrates a triangular shape 501.

FIG. 15 illustrates quadrilateral shapes 601, 602. The shape 601 of view A is convex, as a trapezium. The shape 602 of view B is non-convex.

FIG. 16 illustrates a hexagonal shape and FIG. 17 a five-pointed star.

The plate 2 of certain objects of the invention is such that, if it retains the shape at rest during the period of use, the flow of air F would be incapable of causing rotation of the plate 2 substantially around the axis Iz. This for example is the case of the plate 2 of objects 1, 101, and 201. Indeed, if the plate 2 of these objects was perfectly rigid, the shape during use would be identical with the shape at rest. Because of the symmetries of the plate 2, no rotation of the plate 2 around the Iz axis would occur in the flow of air F.

This rotational property of the objects 1, 101 and 201 gives them a surprising or <<magic>> nature, in the sense that it is the subtle transition from the shape at rest to the shape during use which allows rotation of the plate 2. The plate 2 then becomes a free propeller, only by passing from the position at rest to the position during use. The plate 2 is no longer a free propeller once it has resumed the shape at rest after each period of use.

The objects 1, 101 and 201 are advantageously conformed in order to have the following property. If in the absence of an air draft, the plate 2 is released from a height of at least 2.0 meters, with 0 initial velocity, the plate 2 assuming the shape at rest, the plane P being substantially horizontal and the rear face 4 being oriented downwards, then the plate 2 substantially falls according to a translational movement which is substantially rectilinear and vertical, with an average falling velocity of less than 2.0 m/s, preferably less than 1.5 m/s and even more preferably less than 1.0 m/s.

Further, certain objects according to the invention may, because of their shape at rest, suggest that they will rotate around the Iz axis in a given direction, and finally rotate in the other direction during the periods of use, because of the transition from the shape at rest to the shape in use. For these objects, the shape at rest is a free propeller having a given direction of rotation around the axis Iz, while the shape in use is a free propeller having an opposite direction of rotation around the Iz axis.

According to other alternatives, the plate 2 may have apertures, for example so as to emit a sound during the periods of use, such as a buzz or a hiss.

According to still other alternatives, the majority of the plate 2 may be made extremely flat, the distance d′ between the planes P1 and P2 surrounding the plate 2 (FIG. 3) being for example less than d/10, or even d/50.

According to other alternatives, the main portion 14 and the peripheral portion 10 may comprise grooves, streaks or “guillochages”.

According to an alternative not shown as the object 1, the peripheral portion 10 and/or the main portion 14 of the plate 2 comprise a relief having one or several lines of crests. The lines of crests are either singular or not. Thus, the flexural strength of the plate 2 is on the whole reinforced.

According to another alternative not shown of the object 1, the peripheral portion 10 comprises an outer rim. The outer rim is for example materialized by a singular and enclosed crest line. The rim is of a substantially planar aspect and substantially parallel to the plane P. Thus, the flexural strength of the plate 2 is improved. The object 1 is thus able to rest in contact through this rim at the perimeter on a planar surface. 

1. An object (1; 101; 201) intended to rotate in a flow of air (F), notably for recreational use, comprising a plate (2) with a general planar aspect, globally extending along a plane (P) the plate (2) having a center of inertia (I) and comprising: a rear face (4) including a central area (16) located in the vicinity of the center of inertia (I), on which an operator (6) is intended to exert a pressure force (F1), either directly or via a support, during periods of use of the object (1; 101; 201); a front face (8) intended to receive the flow of air (F) substantially along an axis (Iz) passing through the center of inertia (I) and perpendicular to the plane (P); a peripheral portion (10, 210) encompassing an edge (12) of the plate (2); and a main portion (14) extending between the peripheral portion and including the central area (16); the plate (2) having a stable shape at rest, preferably able to be piled up, and having this shape after each of the periods of use, the plate (2) having, during any of the periods of use, a shape in use such that: the pressure force (F1) exerted by the operator balances a resulting force (F2) exerted by the flow of air (F) on the plate (2), so that the central area (16) remains in contact with the operator (6) or the support, and the flow of air (F) exerts a torque on the plate (2) causing rotation of the plate (2) substantially around the axis (Iz).
 2. The object (1; 101; 201) according to claim 1, characterized in that the plate (2), on at least 90% of the surface area of the rear face (4), has a thickness (e) comprised between 5 and 500 μm, preferably between 10 and 200 μm, and a basis weight comprised between 10 and 200 g/m², preferably between 20 and 100 g/m².
 3. The object (1; 101; 201) according to claim 1, characterized in that the peripheral portion (10, 210) of the plate comprises one or several areas (18, 20, 22, 24, 26, 28, 30, 32) which cannot be developed.
 4. The object (1; 101; 201) according to claim 1, characterized in that the peripheral portions (10, 210) comprises at least one area forming with the plane (P), at rest, an average angle (α, β) greater than or equal to 10°, preferably greater than or equal to 30°.
 5. The object (201) according to claim 1, characterized in that the plate (2) comprises, at rest, at least one convex area (14-211) for which the convexity is oriented from the front face (8) towards the rear face (4), and at least one other convex area (210) for which the convexity is turned from the rear face (4) to the front face (8), so that the plate (2) may be reversibly used by the operator (6).
 6. The object (1; 101; 201) according to claim 1, characterized in that the plate (2), for passing from the position at rest to the position in use, undergoes flexure along a weakness axis (Dl, D2).
 7. The object (1; 101; 201) according to claim 1, characterized in that the shape at rest of the plate (2) is such that, if the plate (2) retained the shape at rest during the period of use, the flow of air (F) would be incapable of causing rotation of the plate (2) substantially around the axis (Iz).
 8. The object (1; 101; 201) according to claim 1, characterized in that the plate (2), in an orthogonal projection on the plane (P), substantially has a general shape taken from the following shapes: triangular (501) rectangular (302), parallelogram (401, 402, 403, 404, 405), trapezoidal (601), four-sided and convex (601, 302, 402), four-sided and concave (305, 602) with the center of inertia (I) being located inside the quadrilateral, convex polygonal (701), star-shaped polygonal (801) with the center of inertia (I) being located inside the star-shaped polygon.
 9. The object (1; 101; 201) according to claim 1, characterized in that the plate (2), in an orthogonal projection on the plane (P), has a polygonal shape including sides with a substantially rectilinear, concave, convex, S or toothed shape.
 10. The object (1; 101; 201) according to claim 1, characterized in that the plate (2) is in plastic polymer, in bio-plastic polymer, in a laminated material comprising a plastic polymer or a bio-plastic polymer, or in tissue paper. 